The spin cycle of a washing machine removes water centrifugally from wet clothes by spinning the clothes at high speed in a spin basket. In order to reduce the possibility of injury to the user during the spin cycle, it is known to use an electronically actuated lock for holding the washing machine lid in the closed position. U.S. Pat. Nos. 6,363,755; 5,823,017; and 5,520,424, assigned to the present assignee and hereby incorporated by reference, describe several locking mechanisms.
In order to prevent tampering with the lock mechanism, for example, by holding the lid open when the lock is actuated, it is known to provide for lid closure sensing to ensure that the lid is in a proper position before the lock mechanism is engaged. Conventional mechanical lid closure switches can often be defeated by wedging the switch open, for example, with the end of a pencil or the like. U.S. Pat. No. 7,251,961, assigned to the assignee of the present invention and hereby incorporated by reference, describes a lid sensor using a magnet and electrical reed switch to detect lid closure. The use of a magnetic actuator reduces the possibility of casual tampering.
US patent application 2012/0312594, hereby incorporated by reference, describes a lock mechanism in which the magnet is incorporated into a hook or striker that engages the latch. Tampering is detected by requiring that the striker physically move a latch element and magnetically move a separate anti-tampering element. Motion of both elements is detected and required before the appliance can be operated. Common sticks or probes for tampering with the latch will not provide the magnetic interaction with the anti-tampering elements and thus may be distinguished from the actual striker.
In each case, the use of a magnetically actuated element renders physical tampering difficult. Nevertheless, such magnetic systems add cost and complexity to the latching mechanism that may not be acceptable in all cases.